The Vox Multi Link Transformer - impedance matcher
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Above, Multi Link speaker cabinets in the Vox Sound Equipment Limited (VSEL) brochure of early 1969. The text reads:
"This unique VOX invention allows you to convert your existing VOX speaker cabinets to achieve the sound of sounds. The transformer ensures a perfect impedance matching of two of more linked cabinets. No more loss in volume when you run two, three or four units from the same amp output. The opportunity for a new era of sound has at last arrived - thanks to VOX.".
The transformer was incorporated as standard in the Multi Link I and II cabs. One could also buy it separately.
The intention was to make the solid state amps, which only had only speaker output socket, more versatile.
The transformer in the Vox Sound Limited (VSL) catalogue of August 1970. The blurb surrounding it is the same as in the VSEL advert.
Note that the free-standing transformers pictured in the adverts have four outputs. Units incorporated in the speaker cabs generally only have two.
Information plates were affixed to indicate what the total impedance of numbers of linked cabs should be. The sum impedance is switchable between 4, 8 and 16 ohms.
A surviving Multi Link transformer - currently in the UK
This unit probably came from a Multi Link speaker cabinet as the tolex is a bit rough and ready - no point taking too much effort if it was not to be seen. Two speaker outputs are provided.